feat: implement toBeEmptyElement

src/matchers/__tests__/to-be-empty-element.test.tsx

@@ -0,0 +1,30 @@
+import React from 'react';
+import { View } from 'react-native';
+import { render, screen } from '../..';
+import '../extend-expect';
+
+test('.toBeEmptyElement', () => {
+  render(
+    <View testID="not-empty">
+      <View testID="empty" />
+    </View>
+  );
+
+  const empty = screen.getByTestId('empty');
+  const notEmpty = screen.queryByTestId('not-empty');
+  const nonExistentElement = screen.queryByTestId('not-exists');
+  const fakeElement = { thisIsNot: 'an html element' };
+
+  expect(empty).toBeEmptyElement();
+  expect(notEmpty).not.toBeEmptyElement();
+
+  expect(() => expect(empty).not.toBeEmptyElement()).toThrow();
+
+  expect(() => expect(notEmpty).toBeEmptyElement()).toThrow();
+
+  expect(() => expect(fakeElement).toBeEmptyElement()).toThrow();
+
+  expect(() => {
+    expect(nonExistentElement).toBeEmptyElement();
+  }).toThrow();
+});

src/matchers/extend-expect.ts

@@ -1,7 +1,9 @@
 /// <reference path="./extend-expect.d.ts" />
 
 import { toBeOnTheScreen } from './to-be-on-the-screen';
+import { toBeEmptyElement } from './to-be-empty-element';
 
 expect.extend({
   toBeOnTheScreen,
+  toBeEmptyElement,
 });

src/matchers/index.tsx

@@ -1 +1,2 @@
 export { toBeOnTheScreen } from './to-be-on-the-screen';
+export { toBeEmptyElement } from './to-be-empty-element';

src/matchers/to-be-empty-element.tsx

@@ -0,0 +1,29 @@
+import { ReactTestInstance } from 'react-test-renderer';
+import { matcherHint, printReceived } from 'jest-matcher-utils';
+import { getHostChildren } from '../helpers/component-tree';
+import { checkHostElement } from './utils';
+
+export function toBeEmptyElement(
+  this: jest.MatcherContext,
+  element: ReactTestInstance
+) {
+  checkHostElement(element, toBeEmptyElement, this);
+
+  const pass = getHostChildren(element).length === 0;
+
+  return {
+    pass,
+    message: () => {
+      return [
+        matcherHint(
+          `${this.isNot ? '.not' : ''}.toBeEmptyElement`,
+          'element',
+          ''
+        ),
+        '',
+        'Received:',
+        `  ${printReceived(element.children)}`,
+      ].join('\n');
+    },
+  };
+}